I've played the battletech MUDs and MUX's a few times, and helos are scary in those. Well, they can be anyway.
As for aqua mechs... just go all Gundam in this game! lol XD
In all seriousness, the water would be the last place I'd wanna go in a mech. One pin-hole in my canopy, and you're dead. Or an armor breach, that limb is useless.